The model 607 was the backhoe attachment built for use on the 642/643 loader. The 607 is rated for 6 ft. dig depth, and 709 is 7ft. That extra depth means the 709 is a heavier attachment and while it will lock on to the QA Bobtach the 643 is going to be very front end heavy, tippy trying to carry it across the ground. Other problem is the necessary lockdown brackets required. A skidloader backhoe attachment needs some type of rigid locking mechanism to lock the backhoe directly to the loader main frame so the lift and tilt cylinders can not move or drift while digging. The brackets used that are bolted to the frame are specfic for each skidloader model, and width of frame of the 607 & 709 are not the same, so locking brackets used to maount the 607 to the 643 will not work to mount the 709 to the 643. Depending on your abilty you might be able to adapt something to accomplish this. Overall you are better off looking for a 607 although they are not as plentiful on the used market.